In manufacturing objects, structures are often connected to each other. For example, in manufacturing an object, such as an aircraft, many different structures are connected to each other to form assemblies for systems in the aircraft. For example, skin panels may be attached to ribs and spars. As another example, floor panels may be connected to support structures in a fuselage to form the floor of a passenger cabin. In connecting structures to each other, different types of connecting systems may be used. One type of connecting system is a fastener system. A fastener system may include one or more fasteners. For example, a fastener for a fastener system may be a screw, a pin, a bolt, and/or a nut.
These fasteners may be used to connect structures to each other. For example, holes may be formed in the structure and nuts and bolts may be installed relative to the holes. Depending on the structures being coupled together and/or the type of fastener system being used, one or more nut plates, brackets, or clips may be utilized in the fastener system. Often, construction of objects or structures such as aircraft requires installation of a large number of such fastener systems, with each hole drilled and part used adding incrementally to the overall cost of the object and/or to the time to manufacture it. Some such fastener systems may require that components be riveted into place on the structure. U.S. Patent Application Publication No. 2014/0283363 (Wilkerson, et al.), the entirety of which is incorporated herein for all purposes, discloses a rivetless anti-rotation nut plate that is designed to resist rotation without the use of rivets by virtue of a nut plate having a non-circular body end that is inserted into a non-circular hole. Such an arrangement allows for use of a conventional bolt having a circular cross-sectional area and a nut having a through-hole with a circular cross-sectional area as well. In other fastener systems involving installing one or more brackets or clips, two or more bolts may be required to sufficiently secure each bracket or clip so as to prevent rotation of the bracket or clip with respect to the structure to which it is attached, which may otherwise occur if the bracket or clip was installed using a single bolt. To keep two parts in the same relative positions using round holes and fasteners with circular cross-sectional areas, multiple conventional fasteners must be used (e.g., at least two) due to rotation about the central axis of the circular bolts and holes.
Carriage bolts have been used in some applications, where the carriage bolt's shank is circular for most of its length, but the portion immediately beneath the head is formed into a square section. Thus, carriage bolts may be self-locking when placed through a square hole. However, square holes are often not ideal for many industrial applications due to stresses and reduced fatigue properties created at sharp corners. Along the same lines, U.S. Pat. No. 1,822,657 (Horton) discloses a modified carriage bolt with a non-round shoulder portion (the portion of the shank's length that is immediately beneath the head of the bolt) having four flat surfaces and four cylindrical surfaces, which forms a shape that is a combination of a parallelogram and an ellipse. Both conventional carriage bolts and the modified bolt disclosed in Horton have limited applicability, typically being configured to prevent rotation of the bolt head to aid in installation of the nut. Other conventional fastening systems may be costly and/or complicated to manufacture, such as those including nuts having projecting tabs formed thereon or therein, an example of which is disclosed in U.S. Pat. No. 4,014,245 (Frye, et al.).